ES2223122T3 - MOISTURE DETECTION. - Google Patents

Abstract

A detection assembly for detecting moisture within an unsaturated permeable soil or soil-like medium is disclosed which includes a funnel 11 having a surface inclined in use to the vertical for distorting the flow streamlines within the medium to cause an increase in fluid content and saturation at points in the permeable medium; a cup 13 beneath the funnel for collecting free fluid from the saturated permeable medium; a sensor 14 for detecting the presence of free fluid formed upon saturation within the permeable medium, and a vent 16 for venting air from said collection means.

Description

Humidity detection.

This invention relates to the detection of humidity.

As used herein, the term "moisture" has a broad meaning and refers to fluids, particularly water, in a porous medium and / or solutes contained in them.

The invention has a particular application, but not exclusive, in agricultural procedures and apparatus for detect when adequate irrigation has been applied to the soil and it will be done reference to such application for illustrative purposes. However, it you will notice that the invention can be used in other applications that involve moisture detection.

There are known devices that can help irrigators to apply the water according to the needs of the plant. These include sensors based on electrical measurements, thermal and matrix suction (gypsum blocks, thermal probes, capacitance and tensiometry probes), and in dielectric measurements or radiation absorption (reflectometry in the temporal domain, neutron dispersion). These sensors have a different price, robustness, precision and complexity of operation.

The present invention aims at provide an alternative to procedures and devices known to detect the arrival of moisture to a point.

In one aspect, this invention consists in general terms, in a procedure to detect the arrival of moisture to a point located inside or below the root zone of a plant that grows in a soil or a soil-like environment unsaturated permeable, characterized in that the procedure It includes:

the placement at the point of a means of distortion of current lines that have a surface that, in practice, it is not vertical to distort the lines of flow stream of fluid particles that travel to through unsaturated soil at the point to cause an increase of the fluid content and to cause saturation at the point by which free fluid is formed therein;

retention of free fluid in means of retention located under the surface, with filtering means that separate a permeable medium in the distortion media from the streamlines of the retention means and allow the free fluid travels from the permeable medium to the media of retention, or from these, depending on the humidity of the medium permeable, including the retention means a cavity filled with air separated from the ground by the filter or the like so that the retention means and the permeable medium remain connected hydraulically, after retention of the free fluid in the means of retention the air comes out of them through a duct substantially rectilinear that extends upwards substantially vertically from the retaining means to the soil surface;

the detection of the presence of free fluid retained in the retention means, thus indicating the detection of the presence of the free fluid the arrival of moisture to the point; Y

signaling the presence of free fluid at a point above the permeable medium to indicate the arrival of moisture to the point.

In another aspect, the invention consists in general terms in a detection mechanism to detect the arrival of moisture to a point located inside or below the area root of a plant that grows in a soil or medium similar to non-saturated permeable soil, characterized in that the mechanism It includes:

means of distortion of the lines of current that have a surface that, in practice, is not vertical to distort the flow stream current lines of fluid particles that travel through a soil not saturated at the point to cause an increase in the content of fluid and to cause saturation at the point by which free fluid form in it;

retention means located under the surface to retain free fluid; a substantially conduit rectilinear that extends substantially vertically upwards from the retention means to the floor surface to output the air from the retention means after retention of the free fluid in them;

filter media that separate a medium permeable in the distortion means of the current lines of the retention means and allow the free fluid to travel from the permeable medium to the retention means, or from these, depending on the moisture of the permeable medium;

detection means to detect the presence of the free fluid retained in the retention means, thus indicating the detection of the presence of the free fluid the arrival of moisture to the point; and signaling means to signal the presence of the free fluid at a point above the permeable medium to indicate that rain or irrigation water has reached depth,

including retention means a cavity filled with air separated from the ground by the filtering means of such so that the hydraulic continuity between the cavity filled with air and The permeable medium is maintained.

As used herein, the expression "flow stream line" refers to the trajectory followed by a particle of fluid that travels to through a permeable medium.

As used herein, the "free fluid" refers to a fluid that has a Free contour and that can be poured.

It is preferable that the procedure includes also the emission of a signal above the permeable medium to indicate that rain or irrigation water has reached the point.

It is also preferable that the surface be concave up. Preferably, the surface is a funnel.

It is also preferable that the free fluid formed after saturation within the permeable medium it is retained in the retention means at the base of the non-vertical surface.

It is also preferable that the presence of fluid free be detected by the detection means placed in the means of retention.

It is also preferable that the retention means include a cavity full of air.

It is also preferable that the mechanism of detection include a housing that holds the funnel and forms a space between them, in which the ventilation means give Air out of the cavity filled with air to that space.

In order that the present invention may be understood and implemented more easily, to Reference will now be made to the accompanying drawings that illustrate a preferred embodiment of the invention, in which:

the figs. 1 and 2 illustrate embodiments preferred of a sensor to plan irrigation according to the present invention;

fig. 3 illustrates the result of an experiment laboratory in which the sensor of fig. 1 was buried to a 50 cm depth in a fine sand and the results compared with measurements made with reflectometry in the domain temporary (TDR), and

fig. 4 illustrates the result of an experiment in which the sensor of fig. 1 was buried in a crop of Alfalfa and the results compared to the measurements made with TDR.

Generally speaking, in a form of preferred embodiment, the irrigation sensor of the present invention it has a funnel-shaped container whose base is attached a sensor that has a conductimetric tank. In a preferred form of the invention, the container is a plastic funnel and there is a sintered glass cylinder fixed inside a bucket of brass at the base of the cone. The conductimetric cell comprises a brass conductive bucket and a long brass conductive pin, each of which is electrically isolated from the other. The plug is mounted inside the glass cylinder sintered These two conductors are electrically connected to an AC source that, in the embodiment preferred, it can be a fluid detector such as the LM1830 manufactured by National Semiconductor.

More specifically, as illustrated in the fig. 1, the brass bucket 13 is located at the base of the container funnel-shaped 11. Sintered glass cylinder 12 is located inside the brass bowl 13. A rubber stopper 17 plug the upper end of the sintered glass cylinder 12 and it has holes drilled to make the plug of brass 14 and the vent tube 16. Electric wires 18 are connected to brass bowl 13 and brass plug 14. A waterproof sealing compound 15 applied to rubber cap 17 electrically insulates the brass plug 14 and its electrical connection ground. The vent tube 16 extends to the surface ground.

In another form of the invention illustrated in the fig. 2, the irrigation sensor 21 has a container 20 substantially in the shape of a wine glass to optimize the convergence of the flow towards the container and minimize the loss due to the capillarity

A bore cylinder 23 is located at the base of the funnel in the form of a glass of wine 20 and is sealed in its inside by a rubber stopper 27 that plugs the end lower funnel. Cap 27 has perforated holes for pass brass pins 24 (illustrated in line with fig. 2 such that only one is visible) and the tube ventilation 26. Electric wires 28 are connected to the brass pins 24. A porous medium 22 encapsulates cylinder 23 in the lower end of the funnel 20. A waterproof insulator 25 applied to the rubber cap 27 along the funnel base 20 electrically insulates brass plugs 24 and their connections electric moisture. The ventilation tube 26 is extended to the space between funnel 20 and outer shell 29 in the The mechanism is housed.

Unlike the arrangement of fig. 1 in which the conductimetric tank has a vent at the level of floor, the ventilation tube 26 gives air to the tank conductimetric 23 to the air chamber between funnel 20 and the outer shell 29. Consequently, no part of the mechanism protrudes from the surface, thus avoiding the problems of mowing that involves the embodiment of fig. 1, in case of Be located in a grassy area.

The containers can have different sizes to adapt to different types of soil.

If the potential background energy produced during irrigation it is approximately the same as energy minimum potential required to produce saturation in the cuvette porous, the sensor may take an unacceptably long time in shoot up To overcome this limitation, a form of the invention may contain suction means to produce a suction in the inside the porous tray. Suction can be applied Continuous or periodic.

In practice, the sensor is placed towards the lower part of the plant's root zone, and activates a alarm or a solenoid valve when the irrigation water has infiltrated to the required depth. The container is filled with soil and is buried with the funnel opening up and inside or below the root zone of the crop.

After irrigation, a part of the unsaturated flow converges on the bottom of the container, causing it there Increase the water content. Whenever the irrigation regime is sufficient to produce a potential background energy greater than a minimum value, the funnel base floor reaches the saturation and water infiltrates through the porous cylinder to partially fill the conductimetric tank. The air displaced to entering the water in the conductimetric tank passes to the surface to through the vent tube in the case of the embodiment of fig. 1, or to the space between the funnel and its housing in the form of embodiment of fig. 2.

The tank is activated as soon as water is present in the cuvette and an alarm or solenoid valve is activated to Cut the watering. Over a period of a few hours, when going drying the soil, the water in the tank is withdrawn back to the floor by capillary suction and the sensor returns to its initial setting Prepared for future irrigation.

The output signal from the detector fluids can be connected to a microprocessor that controls the plan of irrigation or can work in isolation, whereby the irrigator responds to an alarm by cutting the irrigation.

Although the underlying functional principles to the general aspects of the invention will be readily appreciated, to a more detailed explanation of some will be given below theoretical and operational aspects of the two forms of preferred embodiments of the inventions illustrated in figs. one and 2. However, these are not to be construed as limitations of The invention itself.

As indicated above, the containers They can have different sizes to suit different types of ground. Considering the embodiments of figs. 1 and 2, the maximum container size and depth are two parameters that They determine the performance. In these embodiments you must also note that the sides of the container converge towards an area relatively small and that the container is concave up, thereby converging the flow to the bottom of the container. To facilitate this, the sides of the container are inclined towards the flow stream lines to certain humidity detector distance.

A theoretical explanation of the functional characteristics of the humidity detectors of the embodiments illustrated with reference to the potential energies that are put into play.

It is said that wet soil has an energy negative potential because energy is required to extract water held tightly by soil particles. This energy can measured as a suction in centimeters or millimeters of water. So, it is said that a glass of water with a depth of 5 cm has a potential energy of +5 cm, that is, a positive energy water depth equivalent. A soil that is saturated It has an energy of 0 cm. A soil that is wet has a value negative.

As described above, the detector will fires when there is free water in the conductimetric tank. If this shooting can work to cease irrigation activities, the suction in the soil surrounding the humidity detector will be typical of values found above the humidification front during the irrigation. There is thus a minimum background potential energy at which the detector must fire.

The minimum background potential energy needed to produce saturation depends on the size of the container and It depends slightly on the type of soil and the shape of the container. It is determined by the process of convergence of the lines of current around a buried object caused by the interaction of gravity and capillarity.

An object inserted in a permeable medium will cause distortion of the current lines. If the object is set up, the current lines are they will distort inside the object and converge. Where the Streamlines converge, fluid content increases. The larger a specific object, the greater the increase in fluid content

The soil can transport moisture in any direction through capillary suction provided that no there are waterproof barriers on the road, moving moisture in any point at a speed that depends on the spatial gradient in the moisture content and the physical properties of the soil. If the spatial gradient decreases by introducing a partial barrier between wet and dry soil, transport due to the Capillarity will decrease. By increasing the depth of the container decreases fluid transport by capillarity because the sides of the container constitute a partial barrier to the flow.

The dimensions of the shape containers Preferred embodiments of the invention illustrated were chosen so that the increase in fluid content due to the convergence of flow stream lines, such as that of the container base, reach the saturation point.

Moisture detectors forms preferred embodiments illustrated may be considered as potentiometers that "fire" at an energy potential concrete.

As an example, in the irrigation of agricultural soils standard with standard irrigation equipment, it is desirable that the energy Minimum negative background potential is less than -10 cm approximately. In the preferred embodiments that are illustrate, this is achieved by a container that has a diameter of the funnel of approximately 20 cm and a funnel depth of 10 cm approximately.

In short, the minimum background potential energy necessary to produce saturation depends on the size of the container and depends slightly on the type of soil and the shape of the container. Except for very small containers, it is usually less than the potential background energy that is obtained when a soil is irrigated with micro irrigation or sprinkler technologies standard.

The embodiments described above with reference to the drawings suggest that the funnel will be filled with the floor displaced by digging the hole to install the sensor. Another possibility is that the funnel is filled with another porous material that can change the response time of the detection mechanism In particular, the funnel can be filled with high conductivity material and low water retention capacity to shorten the response time for root crops superficial.

Fig. 3 illustrates the evolution of the content of water inside a fine sand in a laboratory tank. The axis horizontal indicates the time elapsed since the beginning of the irrigation. The detector was buried at a depth of 50 cm and the Water content was determined using TDR. Irrigation was applied with a disk permemeter at a rate of 8.4 liters per hour. The stroke 1 is the water content measured near the base of the funnel, the stroke 2 is the average water content in the layer between the surface and 45 cm depth and line 3 is the average water content measured in the area between 55 and 125 cm deep. The dashed line 4 indicates the time in which water was detected inside the tank conductimetric and in which the irrigation stopped. Line 5 indicates the time in which the last part of the water of the conductimetric tank is removed to the ground and the sensor returned to its initial setting.

Fig. 4 illustrates the evolution of the content of water in a bed of alfalfa grown in clay soil. He abscissa axis indicates the time elapsed since the beginning of the irrigation. The detector was buried with the sensor at a depth of 57 cm and water content was determined using TDR. The irrigation is applied with a sprinkler micro diffuser at a rate of 9.5 mm per hour. Trace 1 is the water content measured near the base of the funnel, trace 2 is the average water content in the layer between the surface and a depth of 60 cm and line 3 is the content Water medium measured in the area between 60 and 90 cm deep. The line 4 indicates the time at which water was detected inside the tank conductimetric and in which the irrigation stopped. Along a 24 hour period after irrigation, an amount was applied insignificant ground water located below the sensor due to which the water applied on the surface (71 mm) was retained in the 0 to 60 cm layer and there is no change in the average content of water in the layer of 60 to 90 cm (line 3).

Referring to line 2, since the average water content in the layer from 0 to 60 cm before irrigation was 28.5% and 24 hours after irrigation the average water content was 41%, the water added to the 0 to 60 cm layer was 75 mm approximately, that is (41% - 28.5%) = 12.5% of 600 mm. He water content inside the irrigation sensor (line 1) changed quickly at the moment when water was detected in the tank conductimetric and shortly after stopping the irrigation the content inside the sensor decreased.

Among other preferred embodiments and Applications of the invention include: (a) planning of nutrients / pollution monitoring, (b) drainage and rotation of crops and (c) rain detection and irrigation control. These describe in more detail below:

(a) Nutrient planning / supervision of pollution

So that the sensor of the detection mechanism is "shoot", a small amount of water must be retained in the conductivity vessel located at the base of the funnel. In a form of preferred embodiment, this water is extracted through the tube of ventilation and soluble nutrients such as nitrates The sensors can be placed at the bottom of the root zone to monitor the movement of pollutants agricultural such as salt or pesticides to rivers or bodies of water underground.

Water sample can be collected by hand little after the sensor is triggered, or its collection can be automatic by connecting the vent tube to a suction tube and opening a solenoid valve in reaction to the water detection in the tank.

This procedure constitutes an improvement with regarding the known sampling procedures that they use ceramic suction cups connected to a suction tube or taking soil samples, diluting them with water and filtering them.

(b) Drainage and crop rotation

The amount of water that moves under the area root of crops is extremely difficult to measure even with a sophisticated team. A useful approach to drainage is the time that a layer of soil has been saturated or close to the saturation. The period of time during which the sensor detects Water in the conductimetric tank provides this information.

This has an application for irrigators and rainfed farmers. For example, cereal farmers You can use this application to decide when to move from a crop from surface roots to a rooting grass crop deep once a certain amount of water has reached the deep underground.

(c) Water detection and irrigation control

Most irrigation controllers apply water at a predetermined time interval. This interval of Time must be adjusted if it rains before a scheduled watering. Yes it rains enough for the detector mechanism to detect water, the irrigation interval can be postponed. This prevents watering. in excess, or irrigation during rains.

It will be appreciated that the present invention has several advantages over systems and procedures known moisture detection.

The application of excess water for Plant needs constitute a worldwide problem. He excess irrigation wastes a resource that is scarce and can contribute to groundwater pollution when the water seeps below the roots of plants transports products agricultural chemicals or mobilizes salt. Excess watering occurs frequently because the cost and / or complexity of measuring soil water to facilitate irrigation decisions with cause knowledge and irrigation control is usually above of the resources or capacity of most users of the Water.

The cost and complexity increase because it is difficult to make precise measurements in situ of the water content of the soil. The present invention overcomes the difficulty of measuring water content in an unsaturated state by forcing soil saturation at a given point.

The sensor output is activated only when sufficient irrigation water has been provided. Thus, it is not necessary that the output is interpreted or analyzed, as is the case with the output of devices that measure partial saturation instead of the total.

What's more, since saturation detection is technically trivial, the sensor of the present invention is relatively cheap to manufacture, and it is robust and durable.

Of course, it will be understood that while above has been explained as an illustrative example of the present invention, all these and other modifications and variations of it, as is obvious to experts in the matter, are considered within the general scope and scope of the present invention as set forth herein document.

Claims (11)

1. A procedure to detect the arrival of moisture at a point located inside or below the root zone of a plant that grows in a soil or medium similar to the unsaturated permeable soil, characterized in that said procedure includes: the placement at said point of means of distortion of the current lines (11) that have a surface which, in practice, is not vertical to distort the lines of flow stream of fluid particles that travel to through unsaturated soil at that point to cause a increased fluid content and to cause saturation in said point by which free fluid is formed therein; the retention of said free fluid in means of retention (13) located under said surface, separating some filter media (12) a permeable medium in the media of distortion of the current lines (11) of the means of retention (13) and allowing the free fluid to travel from the permeable medium to the retention means (13), or from these, depending on the moisture of the permeable medium, including the retention means (13) a cavity filled with air separated from the soil by the filtering means (12) or the like, such that the retention means (13) and the permeable medium remain hydraulically connected, after retention of free fluid in the retention means (13) the air leaves from there through a substantially rectilinear duct (15) extending towards above substantially vertically from said retaining means (13) to the ground surface; the detection of the presence of free fluid retained in the retention means (13), the detection of the presence of the free fluid thus indicating the arrival of moisture to said point; and signaling the presence of free fluid in a point above the permeable medium to indicate arrival of humidity at that point. 2. A procedure to detect the arrival of humidity according to claim 1, and which includes the emission of a signal above the permeable medium to indicate that the rain or the irrigation water has reached that point. 3. A procedure to detect the arrival of moisture according to claim 1, wherein said surface is concave up. 4. A procedure to detect the arrival of moisture according to claim 1, wherein the free fluid formed after saturation inside the permeable medium it is retained in some retention means located at the base of the surface not vertical. 5. A procedure to detect the arrival of humidity according to claim 4, wherein the presence of fluid free is detected by means of detection (14) placed in the means of retention. 6. A detection mechanism for detecting the arrival of moisture at a point located inside, or below the root zone of a plant that grows in a soil or a medium similar to the unsaturated permeable soil, characterized in that said mechanism includes: means of distortion of the lines of current (11) that have a surface that, in practice, is not vertical to distort the flow stream current lines of fluid particles that travel through a soil not saturated at that point to cause an increase in the content of fluid and to cause saturation at that point by which free fluid is formed therein; retention means (13) located under said surface for retaining said free fluid; a substantially rectilinear conduit (16) that extends up substantially vertically from said retaining means to the floor surface to exit the air of said retention means (13) after fluid retention free in them; filtering means (12) separating a medium permeable in the distortion means of the current lines (11) of the retention means (13) and allow the free fluid travel from the permeable medium to the retention means, or from these, depending on the moisture of the permeable medium; detection means (14) to detect the presence of the free fluid retained in the retention means, thus indicating the detection of the presence of the free fluid the arrival of moisture at that point; Y signaling means (18) for signaling the presence of the free fluid at a point above the permeable medium to indicate that rain or irrigation water has reached that depth, said retention means including a cavity filled with air separated from the ground by the filtering means of such way that the hydraulic continuity between the cavity is maintained Full of air and permeable medium. 7. A detection mechanism according to the claim 6, wherein said surface is concave toward above. 8. A detection mechanism according to the claim 7, wherein said surface is a funnel. 9. A detection mechanism according to the claim 8, wherein said retention means include a air filled cavity. 10. A detection mechanism according to the claim 8, and including a housing (29) that holds said funnel and forms a space between them, in which said means of ventilation give air out of said cavity filled with air to said space. 11. A detection mechanism according to claim 6, wherein said detection means includes sensor means placed in the retention means.